Electronic component and selection method

ABSTRACT

In an electronic component, a laminate is obtained by laminating a plurality of ceramic layers, and includes an upper surface and a bottom surface which are at ends of the laminate in the z-axis direction, end surfaces facing each other, and side surfaces facing each other. First capacitor conductors, second capacitor conductors, and the ceramic layers are laminated. One of the first capacitor conductors and one of the second capacitor conductors face each other via one of the ceramic layers. A first external electrode and a second external electrode are located on one of the end surfaces and one of the side surfaces, respectively, and are connected to the first capacitor conductors. A third external electrode and a fourth external electrode are located on the other one of the end surfaces and the other one of the side surfaces, respectively, and are connected to the second capacitor conductors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electronic components and selection methods, and, more particularly, to an electronic component including a capacitor and a selection method.

2. Description of the Related Art

In an electronic component in which a dielectric layer and a capacitor conductor are laminated, when an alternating voltage is applied to the electronic component, the alternating voltage generates an electric-field-induced strain at the dielectric layer. The electric-field-induced strain vibrates a substrate on which the electronic component is mounted and generates a sound called an acoustic noise. Examples of an electronic component with which such a “squeal” is suppressed include the method of mounting a multilayer ceramic capacitor on a circuit board disclosed in Japanese Unexamined Patent Application Publication No. 2000-232030.

As disclosed in Japanese Unexamined Patent Application Publication No. 2000-232030, capacitors that meet the same specifications are disposed on the surface and undersurface of a circuit board. A vibration transmitted from one of the capacitors to the circuit board and a vibration transmitted from the other one of the capacitors to the circuit board cancel each other. As a result, an acoustic noise is suppressed.

However, since two capacitors have to be disposed on both surfaces of a circuit board as disclosed in Japanese Unexamined Patent Application Publication No. 2000-232030, the degree of circuit design freedom is limited.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide an electronic component and a selection method which are capable of providing a high degree of circuit design freedom and suppressing an acoustic noise.

An electronic component according to a preferred embodiment of the present invention includes a laminate that is a substantially rectangular parallelepiped, includes a plurality of laminated dielectric layers, and includes an upper surface and a bottom surface which are at both ends of the laminate in a lamination direction, a first end surface and a second end surface facing each other, and a first side surface and a second side surface facing each other, a first capacitor conductor and a second capacitor conductor that are laminated with the dielectric layer and face each other via the dielectric layer, a first external electrode and a second external electrode that are disposed on the first end surface and the first side surface, respectively, and are connected to the first capacitor conductor, and a third external electrode and a fourth external electrode that are disposed on the second end surface and the second side surface, respectively, and are connected to the second capacitor conductor. On the first end surface and the first side surface, no external electrode held at a potential different from a potential at which the first and second external electrodes are held is disposed between the first and second external electrodes. On the second end surface and the second side surface, no external electrode held at a potential different from a potential at which the third and fourth external electrodes are held is disposed between the third and fourth external electrodes.

A selection method according to another preferred embodiment of the present invention is a method of selecting external electrodes to be used for mounting of the above-described electronic component on a circuit board including first to fourth land electrodes corresponding to the first to fourth external electrodes from among the first to fourth external electrodes. The selection method includes connecting the first and third external electrodes to the first and third land electrodes, respectively, in a case where sound generated by vibration of the circuit board when the first and third external electrodes are connected to the first and third land electrodes, respectively is smaller than that generated by vibration of the circuit board when the second and fourth external electrodes are connected to the second and fourth land electrodes, respectively and connecting the second and fourth external electrodes to the second and fourth land electrodes, respectively in a case where sound generated by vibration of the circuit board when the second and fourth external electrodes are connected to the second and fourth land electrodes, respectively is smaller than that generated by vibration of the circuit board when the first and third external electrodes are connected to the first and third land electrodes, respectively.

According to various preferred embodiments of the present invention, it is possible to obtain a high degree of circuit design freedom and suppress an acoustic noise.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of an electronic component according to a preferred embodiment of the present invention.

FIG. 2 is an exploded perspective view of a laminate in the electronic component illustrated in FIG. 1.

FIG. 3 is an external perspective view of a circuit board.

FIG. 4A is a diagram illustrating a state in which the circuit board resonates in a first resonant mode.

FIG. 4B is a diagram illustrating a state in which the circuit board resonates in a second resonant mode.

FIGS. 5A and 5B are plan views illustrating exemplary states in which the electronic component is mounted on the circuit board.

FIGS. 6A and 6B are plan views illustrating other exemplary states in which the electronic component is mounted on the circuit board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An electronic component according to a preferred embodiment of the present invention and a selection method according to another preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

First, the structure of an electronic component according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an external perspective view of an electronic component 10 according to a preferred embodiment of the present invention. FIG. 2 is an exploded perspective view of a laminate 11 in the electronic component 10 illustrated in FIG. 1. In the following description, a lamination direction in the laminate 11 is defined as a z-axis direction. A direction in which the long sides of the laminate 11 extend in plan view of the laminate 11 from the z-axis direction is defined as an x-axis direction. A direction in which the short sides of the laminate 11 extend in plan view of the laminate 11 from the z-axis direction is defined as a y-axis direction.

The electronic component 10 preferably is a chip capacitor, for example, and is mounted on a circuit board as illustrated in FIG. 1. As illustrated in FIGS. 1 and 2, the electronic component 10 includes the laminate 11, external electrodes 12 (12 a to 12 d), capacitor conductors 30 (30 a to 30 d) and 32 (32 a to 32 d) (not illustrated in FIG. 1).

As illustrated in FIG. 1, the laminate 11 is a substantially rectangular parallelepiped including an upper surface S1, a bottom surface S2, end surfaces S3 and S4 facing each other, and side surfaces S5 and S6 facing each other. The upper surface S1 and the bottom surface S2 are at both ends of the laminate 11 in the z-axis direction. Since chamfering is performed on the laminate 11, the laminate 11 has substantially round-shaped corners and ridge lines. In the following description, it is assumed that the upper surface S1 extends in the positive z-axis direction, the bottom surface S2 extends in the negative z-axis direction, the end surface S3 extends in the negative x-axis direction, the end surface S4 extends in the positive x-axis direction, the side surface S5 extends in the negative y-axis direction, and the side surface S6 extends in the positive y-axis direction in the laminate 11. The bottom surface S2 is a surface that faces a circuit board when the electronic component 10 is mounted on the circuit board.

The longitudinal direction of the laminate 11 is in the x-axis direction. A distance L1 between the end surfaces S3 and S4 and a distance L2 between the side surfaces S5 and S6 differ from each other. More specifically, the distance L1 is longer than the distance L2.

As illustrated in FIG. 2, the laminate 11 is obtained by laminating a plurality of ceramic layers (dielectric layers) 17 (17 a to 17 n) from the positive z-axis direction to the negative z-axis direction in this order. The ceramic layers 17 preferably are substantially rectangular in shape, and are made of a dielectric ceramic, for example. In the following description, the main surface of the ceramic layer 17 in the positive z-axis direction is called a surface and the main surface of the ceramic layer 17 in the negative z-axis direction is called an undersurface.

The upper surface S1 of the laminate 11 is the surface of the ceramic layer 17 a extending in the most positive z-axis direction. The bottom surface S2 of the laminate 11 is the undersurface of the ceramic layer 17 n extending in the most negative z-axis direction. The end surface S3 includes the short sides of the ceramic layers 17 a to 17 n in the negative x-axis direction. The end surface S4 includes the short sides of the ceramic layers 17 a to 17 n in the positive x-axis direction. The side surface S5 includes the long sides of the ceramic layers 17 a to 17 n in the negative y-axis direction. The side surface S6 includes the long sides of the ceramic layers 17 a to 17 n in the positive y-axis direction.

The capacitor conductors 30 a to 30 d and 32 a to 32 d and the ceramic layers 17 are laminated, so that the capacitor conductors 30 a to 30 d and the capacitor conductors 32 a to 32 d face, respectively via corresponding one of the ceramic layers 17. The capacitor conductors 30 a to 30 d and 32 a to 32 ddefine a capacitor C.

As illustrated in FIG. 2, the capacitor conductors 30 a to 30 d are disposed on the surfaces of the ceramic layers 17 d, 17 f, 17 h, and 17 j, respectively, and are included in the laminate 11. The capacitor conductors 30 a to 30 d include capacitor portions 40 a to 40 d, lead portions 50 a to 50 d, and lead portions 52 a to 52 d, respectively. The capacitor portions 40 a to 40 d preferably are substantially rectangular in shape. The lead portions 50 a to 50 d are connected to the capacitor portions 40 a to 40 d, respectively, and extend to the short sides of the ceramic layers 17 d, 17 f, 17 h, and 17 j in the negative x-axis direction, respectively. As a result, as illustrated in FIG. 1, the lead portions 50 a to 50 d extend to the end surface S3 (first end surface). The lead portions 52 a to 52 d are connected to the capacitor portions 40 a to 40 d, respectively, and extend to the long sides of the ceramic layers 17 d, 17 f, 17 h, and 17 j in the negative y-axis direction, respectively. As a result, as illustrated in FIG. 1, the lead portions 52 a to 52 d extend to the side surface S5 (first side surface).

As illustrated in FIG. 2, the capacitor conductors 32 a to 32 d are disposed on the surfaces of the ceramic layers 17 e, 17 g, 17 i, and 17 k, respectively, and are included in the laminate 11. The capacitor conductors 32 a to 32 d include capacitor portions 42 a to 42 d, lead portions 54 a to 54 d, and lead portions 56 a to 56 d, respectively. The capacitor portions 42 a to 42 d preferably are substantially rectangular in shape, and face the capacitor portions 40 a to 40 d via the ceramic layers 17 d, 17 f, 17 h, and 17 j, respectively. The lead portions 54 a to 54 d are connected to the capacitor portions 42 a to 42 d, respectively, and extend to the short sides of the ceramic layers 17 e, 17 g, 17 i, and 17 k in the positive x-axis direction, respectively. As a result, as illustrated in FIG. 1, the lead portions 54 a to 54 d extend to the end surface S4 (second end surface). The lead portions 56 a to 56 d are connected to the capacitor portions 42 a to 42 d, respectively, and extend to the long sides of the ceramic layers 17 e, 17 g, 17 i, and 17 k in the positive y-axis direction, respectively. As a result, as illustrated in FIG. 1, the lead portions 56 a to 56 d extend to the side surface S6 (second side surface).

The external electrode 12 a (first external electrode) is disposed on the end surface S3, and is folded back on the upper surface S1, the bottom surface S2, and the side surfaces S5 and S6. The external electrode 12 a entirely covers the end surface S3 of the laminate 11 so that it covers the portions of the lead portions 50 a to 50 d exposed on the end surface S3. As a result, the external electrode 12 a is connected to the capacitor conductors 30 a to 30 d.

The external electrode 12 b (third external electrode) is disposed on the end surface S4, and is folded back on the upper surface S1, the bottom surface S2, and the side surfaces S5 and S6. The external electrode 12 b entirely covers the end surface S4 of the laminate 11 so that it covers the portions of the lead portions 54 a to 54 d exposed on the end surface S4. As a result, the external electrode 12 b is connected to the capacitor conductors 32 a to 32 d.

The external electrode 12 c (second external electrode) is disposed on the side surface S5, and is folded back on the upper surface S1 and the bottom surface S2. The external electrode 12 c covers the portions of the lead portions 52 a to 52 d exposed on the side surface S5. As a result, the external electrode 12 c is connected to the capacitor conductors 30 a to 30 d.

The external electrode 12 d (fourth external electrode) is disposed on the side surface S6, and is folded back on the upper surface S1 and the bottom surface S2. The external electrode 12 d covers the portions of the lead portions 56 a to 56 d exposed on the side surface S6. As a result, the external electrode 12 d is connected to the capacitor conductors 32 a to 32 d.

The external electrodes 12 a and 12 c are held at the same potential, and the external electrodes 12 b and 12 d are held at the same potential. On the end surface S3 and the side surface S5, no external electrode that is held at a potential different from the potential of the external electrodes 12 a and 12 c is disposed between the external electrodes 12 a and 12 c. On the end surface S4 and the side surface S6, no external electrode that is held at a potential different from the potential of the external electrodes 12 b and 12 d is disposed between the external electrodes 12 b and 12 d. In the present preferred embodiment, on the end surfaces S3 and S4 and the side surfaces S5 and S6, no external electrodes other than the external electrodes 12 a to 12 d are disposed.

Next, the structure of a circuit board on which the electronic component 10 is mounted will be described with reference to the accompanying drawing. FIG. 3 is an external perspective view of a circuit board 100.

The circuit board 100 is a multilayer substrate including circuits thereon and therein, and is provided with a substrate body 102 and land electrodes 104 (104 a to 104 d) as illustrated in FIG. 3. The substrate body 102 is obtained by laminating a plurality of insulating layers, and preferably is substantially rectangular in shape. The long sides of the substrate body 102 are parallel or substantially parallel to the x-axis direction, and the short sides of the substrate body 102 are parallel to the y-axis direction.

The land electrodes 104 a to 104 d are disposed on the substrate body 102. More specifically, as illustrated in FIG. 3, the land electrodes 104 a and 104 b preferably are substantially rectangular in shape in plan view from the z-axis direction and are arranged in this order from the negative x-axis direction to the positive x-axis direction. As illustrated in FIG. 3, the land electrodes 104 c and 104 d preferably are substantially rectangular in shape in plan view from the z-axis direction and are arranged in this order from the negative y-axis direction to the positive y-axis direction. The land electrodes 104 a to 104 d are soldered to the external electrodes 12 ato 12 d, respectively. As will be described later, all of the external electrodes 12 a to 12 d are not connected to the land electrodes 104 a to 104 d, respectively. External electrodes to be used are selected from among the external electrodes 12 a to 12 d, and the selected external electrodes are individually connected to corresponding ones of the land electrodes 104 a to 104 d.

The circuit board 100 has a plurality of resonant modes. FIG. 4A is a diagram illustrating a state in which the circuit board 100 resonates in a first resonant mode. FIG. 4B is a diagram illustrating a state in which the circuit board 100 resonates in a second resonant mode.

Before the first and second resonant modes are described, the detailed structure of the circuit board 100 will be described. The circuit board 100 preferably has a size of approximately 100 mm×40 mm×1.6 mm, for example. The Young's modulus of the circuit board 100 preferably is approximately 17 GPa, and the Poisson's ratio of the circuit board 100 is approximately 0.2, for example.

As illustrated in FIG. 4A, the first resonant mode is a mode in which the circuit board 100 resonates while bending the long sides thereof extending in the x-axis direction. In the first resonant mode, both ends of the circuit board 100 in the x-axis direction become nodes of vibration and the center of the circuit board 100 in the x-axis direction becomes an antinode of vibration. The length of the circuit board 100 in the x-axis direction is equivalent to the half-wavelength of a wave propagating through the circuit board 100. A resonant frequency in the first resonant mode preferably is approximately 500 Hz, for example. The first resonant mode is set when the external electrodes 12 a and 12 b are soldered to the land electrodes 104 a and 104 b, respectively and an alternating voltage having a frequency close to approximately 500 Hz is applied to the electronic component 10.

As illustrated in FIG. 4B, the second resonant mode is a mode in which the circuit board 100 resonates while bending the short sides thereof extending in the y-axis direction. In the second resonant mode, both ends of the circuit board 100 in the y-axis direction become nodes of vibration and the center of the circuit board 100 in the y-axis direction becomes an antinode of vibration. The length of the circuit board 100 in the y-axis direction is equivalent to the half-wavelength of a wave propagating through the circuit board 100. A resonant frequency in the second resonant mode preferably is approximately 3.2 kHz, for example. The second resonant mode is set when the external electrodes 12 c and 12 d are soldered to the land electrodes 104 c and 104 d, respectively and an alternating voltage having a frequency close to approximately 3.2 kHz is applied to the electronic component 10.

When the first or second resonant mode is set, an acoustic noise occurs. In the electronic component 10 and a selection method according to a preferred embodiment of the present invention, in order to suppress an acoustic noise, external electrodes to be used for the mounting of the electronic component 10 on the circuit board 100 are selected from among the external electrodes 12 a to 12 d. FIGS. 5A and 5B are plan views illustrating exemplary states in which the electronic component 10 is mounted on the circuit board 100. Referring to FIG. 5A, the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b, respectively. Referring to FIG. 5B, the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d, respectively.

In a case where sound (an acoustic noise) generated by the vibration of the circuit board 100 when the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b, respectively is smaller than that generated by the vibration of the circuit board 100 when the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d, respectively, the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b, respectively. On the other hand, in a case where sound (an acoustic noise) generated by the vibration of the circuit board 100 when the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d, respectively, is smaller than that generated by the vibration of the circuit board 100 when the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b, respectively, the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d, respectively.

For example, the absolute value of a difference between a frequency f1 of an alternating voltage applied to the electronic component 10 and the resonant frequency (that is, the resonant frequency in the first resonant mode: approximately 500 Hz) of the circuit board 100 in the x-axis direction in which the land electrodes 104 a and 104 b are arranged is larger than that of a difference between the frequency f1 of the alternating voltage and the resonant frequency (that is, the resonant frequency in the second resonant mode: approximately 3.2 kHz) of the circuit board 100 in the y-axis direction in which the land electrodes 104 c and 104 d are arranged, the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b via solder portions 110 a and 110 b, respectively as illustrated in FIG. 5A. In this preferred embodiment, in a case where the frequency f1 of an alternating voltage is higher than approximately 1.85 kHz, the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b via the solders 110 a and 110 b, respectively.

On the other hand, the absolute value of the difference between the frequency f1 of an alternating voltage and the resonant frequency in the first resonant mode is smaller than that of the difference between the frequency f1 of the alternating voltage and the resonant frequency in the second resonant mode, the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d via solders 110 c and 110 d, respectively as illustrated in FIG. 5B. In the present preferred embodiment, in a case where the frequency f1 of an alternating voltage is lower than approximately 1.85 kHz, the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d via the solders 110 c and 110 d, respectively.

Next, a non-limiting example of a method of manufacturing the electronic component 10 will be described with reference to FIGS. 1 and 2.

First, a binder and an organic solvent are added to ceramic powder such as BaTiO₃. These materials are input into a ball mill and are wet-mixed, so that ceramic slurry is obtained. The obtained ceramic slurry is formed on a carrier sheet in the form of a sheet by the doctor blade method and is then dried, so that a ceramic green sheet to be the ceramic layer 17 is created. It is desired that the thickness of a ceramic green sheet to be the ceramic layer 17 be in the range of approximately 0.5 μm to approximately 10 μm after firing. The ceramic powder may contain CaTiO₃, SrTiO₃, or CaZrO₃ as a main component, and may contain an Mn compound, an Mg compound, an Si compound, a Co compound, an Ni compound, or a rare-earth compound as an accessory component.

Subsequently, a paste made of a conductive material is applied to ceramic green sheets, which are to be the ceramic layers 17, by screen printing, so that the capacitor conductors 30 and 32 are formed. The paste made of the conductive material is obtained by adding an organic binder and an organic solvent to metal powder such as Ni, Cu, Ag, Pd, an Ag—Pd alloy, or Au. It is desired that the thicknesses of the capacitor conductors 30 and 32 be in the range of approximately 0.3 μm to approximately 2.0 μm after firing, for example.

Subsequently, the ceramic green sheets, which are to be the ceramic layers 17, are laminated to obtain a green mother laminate. The green mother laminate is compressed.

Subsequently, the green mother laminate is cut into a plurality of green laminates 11 each having a predetermined size. The surface of the green laminate 11 is subjected to polishing such as barrel polishing.

Subsequently, the green laminate 11 is fired. For example, the firing temperature is in the range of approximately 1200° C. to approximately 1300° C., for example.

Subsequently, the external electrodes 12 are formed at the laminate 11. More specifically, a conductive paste containing Cu, Ni, Ag, Pd, an Ag—Pd alloy, or Au is applied to the surface of the laminate 11 by a dip method or a slit method in the related art. A base electrode is formed by baking, and is subjected to Ni plating and Sn plating. As a result, the external electrodes 12 are formed. Through the above-described process, the electronic component 10 is formed.

The electronic component 10 having the above-described structure is mounted on the circuit board 100. The substrate body 102 of the circuit board 100 is obtained by laminating a plurality of insulating layers made of, for example, glass epoxy. The land electrode 104 is obtained by plating a base electrode made of Cu. First, external electrodes to be used for mounting are selected from among the external electrodes 12. Subsequently, a solder paste is applied to the land electrodes 104 corresponding to the selected external electrodes 12. Subsequently, the external electrodes 12 are arranged on the land electrodes 104 so that the bottom surface S2 faces the main surface of the substrate body 102 in the positive z-axis direction. Subsequently, the solder paste is melted by reflowing and is then hardened. As a result, the electronic component 10 is mounted on the circuit board 100.

For example, as the solder paste, Sn—Pb eutectic solder or lead-free solder such as Sn—Ag—Cu solder can be used. Instead of the solders 110, a conductive adhesive may be used.

With the electronic component 10 and the above-described selection method, an acoustic noise can be suppressed as will be described below. More specifically, at the circuit board 100 on which the electronic component 10 is mounted, the first resonant mode and the second resonant mode may occur. The first resonant mode is a mode in which the circuit board 100 resonates while bending the long sides thereof extending in the x-axis direction as illustrated in FIG. 4A. A resonant frequency in the first resonant mode is, for example, approximately 500 Hz. The second resonant mode is a mode in which the circuit board 100 resonates while bending the short sides thereof extending in the y-axis direction as illustrated in FIG. 4B. A resonant frequency in the second resonant mode is, for example, approximately 3.2 kHz.

In the electronic component 10, the external electrodes 12 a and 12 c are disposed on the end surface S3 and the side surface S5, respectively, and are connected to the capacitor conductors 30 a to 30 d. The external electrodes 12 b and 12 d are disposed on the end surface S4 and the side surface S6, respectively, and are connected to the capacitor conductors 32 a to 32 d. As external electrodes to be used for the mounting of the electronic component 10 on the circuit board 100, the external electrodes 12 a and 12 b or the external electrodes 12 c and 12 d can be selected. In a case where the absolute value of a difference between the frequency f1 of an alternating voltage applied to the electronic component 10 and the resonant frequency (approximately 500 Hz) in the first resonant mode is larger than that of a difference between the frequency f1 of the alternating voltage and the resonant frequency (approximately 3.2 kHz) in the second resonant mode, the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b via the solders 110 a and 110 b, respectively as illustrated in FIG. 5A. As a result, when the alternating voltage is applied to the electronic component 10, the occurrence of the second resonant mode is suppressed. In a case where the absolute value of a difference between the frequency f1 of an alternating voltage and the resonant frequency in the first resonant mode is smaller than that of a difference between the frequency f1 of the alternating voltage and the resonant frequency in the second resonant mode, the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d via the solders 110 c and 110 d, respectively as illustrated in FIG. 5B. As a result, when the alternating voltage is applied to the electronic component 10, the occurrence of the first resonant mode is suppressed. Thus, with the electronic component 10 and the selection method, the occurrence of the first resonant mode and the second resonant mode is suppressed and an acoustic noise is suppressed.

Furthermore, in the electronic component 10 and the selection method, two capacitors are not needed unlike in the method disclosed in Japanese Unexamined Patent Application Publication No. 2000-232030. Accordingly, a high degree of circuit design freedom can be obtained.

The electronic component 10 according to a preferred embodiment of the present invention and a selection method according to another preferred embodiment of the present invention can be changed within the scope of the present invention.

In the electronic component 10 and the above-described selection method, a connection pattern illustrated in FIG. 5A in which the external electrodes 12 a and 12 b are connected to the land electrodes 104 a and 104 b, respectively or a connection pattern illustrated in FIG. 5B in which the external electrodes 12 c and 12 d are connected to the land electrodes 104 c and 104 d, respectively is preferably selected. However, other connection patterns can be considered with the external electrodes 12 a to 12 d and the land electrodes 104 a to 104 d. FIGS. 6A and 6B are plan views illustrating other exemplary states in which the electronic component 10 is mounted on the circuit board 100.

Referring to FIG. 6A, the external electrodes 12 a and 12 d are connected to the land electrodes 104 a and 104 d, respectively. Referring to FIG. 6B, the external electrodes 12 b and 12 c are connected to the land electrodes 104 b and 104 c, respectively. In a case where the frequency f1 of an alternating voltage is close to both the resonant frequency in the first resonant mode and the resonant frequency in the second resonant mode, these connection patterns can be used.

The above-described selection method may be performed in the process of design of the electronic component and the circuit board 100. More specifically, in the process of design, external electrodes with which the occurrence of the first and second resonant modes is suppressed are selected from among the external electrodes 12 a to 12 d. At the time of manufacturing, only ones of the land electrodes 104 a to 104 d corresponding to the selected ones of the external electrodes 12 a to 12 d may be formed at the circuit board 100.

Various preferred embodiments of the present invention are useful for an electronic component and a selection method, and, in particular, has an advantage in its suitability for providing a high degree of circuit design freedom and suppressing an acoustic noise.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. An electronic component comprising: a laminate including a plurality of laminated dielectric layers, an upper surface and a bottom surface which are at both ends of the laminate in a lamination direction, a first end surface and a second end surface facing each other, and a first side surface and a second side surface facing each other; a first capacitor conductor and a second capacitor conductor that are laminated with the dielectric layers and face each other with one of the dielectric layers disposed therebetween; a first external electrode and a second external electrode that are disposed on the first end surface and the first side surface, respectively, and are connected to the first capacitor conductor; and a third external electrode and a fourth external electrode that are disposed on the second end surface and the second side surface, respectively, and are connected to the second capacitor conductor; wherein on the first end surface and the first side surface, no external electrode held at a potential different from a potential at which the first and second external electrodes are held is disposed between the first and second external electrodes; and on the second end surface and the second side surface, no external electrode held at a potential different from a potential at which the third and fourth external electrodes are held is disposed between the third and fourth external electrodes.
 2. The electronic component according to claim 1, wherein a distance between the first and second end surfaces is different from a distance between the first and second side surfaces.
 3. A selection method of selecting external electrodes to be used for mounting of the electronic component according to claim 1 on a circuit board including first to fourth land electrodes corresponding to the first to fourth external electrodes from among the first to fourth external electrodes, the method comprising: connecting the first and third external electrodes to the first and third land electrodes, respectively in a case where sound generated by vibration of the circuit board when the first and third external electrodes are connected to the first and third land electrodes, respectively is smaller than that generated by vibration of the circuit board when the second and fourth external electrodes are connected to the second and fourth land electrodes, respectively; and connecting the second and fourth external electrodes to the second and fourth land electrodes, respectively in a case where sound generated by vibration of the circuit board when the second and fourth external electrodes are connected to the second and fourth land electrodes, respectively is smaller than that generated by vibration of the circuit board when the first and third external electrodes are connected to the first and third land electrodes, respectively.
 4. The selection method according to claim 3, further comprising: connecting the first and third external electrodes to the first and third land electrodes, respectively in a case where an absolute value of a difference between a frequency of an alternating voltage applied to the electronic component and a first resonant frequency of the circuit board in a first direction in which the first and third land electrodes are arranged is larger than that of a difference between the frequency of the alternating voltage and a second resonant frequency of the circuit board in a second direction in which the second and fourth land electrodes are arranged; and connecting the second and fourth external electrodes to the second and fourth land electrodes, respectively in a case where the absolute value of the difference between the frequency of the alternating voltage and the first resonant frequency is smaller than that of the difference between the frequency of the alternating voltage and the second resonant frequency. 